Zircon

Zircon
A lustrous crystal of zircon perched on a tan matrix of calcite from the Gilgit District of Pakistan
General
Category	Nesosilicates
Formula (repeating unit)	zirconium silicate (ZrSiO4)
IMA symbol	Zrn[1]
Strunz classification	9.AD.30
Crystal system	Tetragonal
Crystal class	Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m)
Space group	I41/amd (No. 141)
Unit cell	a = 6.607(1), c = 5.982(1) [Å]; Z = 4
Identification
Color	Reddish brown, yellow, green, blue, gray, colorless; in thin section, colorless to pale brown
Crystal habit	tabular to prismatic crystals, irregular grains, massive
Twinning	On {101}. Crystals shocked by meteorite impact show polysynthetic twins on {112}
Cleavage	{110} and {111}
Fracture	Conchoidal to uneven
Tenacity	Brittle
Mohs scale hardness	7.5
Luster	Vitreous to adamantine; greasy when metamict.
Streak	White
Diaphaneity	Transparent to opaque
Specific gravity	4.6–4.7
Optical properties	Uniaxial (+)
Refractive index	nω = 1.925–1.961 nε = 1.980–2.015, 1.75 when metamict
Birefringence	δ = 0.047–0.055
Pleochroism	Weak
Fusibility	close to 2,550 °C depend on Hf,Th,U,H,etc... concentrations.
Solubility	Insoluble
Other characteristics	Fluorescent and radioactive, May form pleochroic halos, Relief: high
References	[2][3][4][5][6]

Zircon (/ˈzɜːrkɒn, -kən/)^[7][8][9] is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is ZrSiO₄. An empirical formula showing some of the range of substitution in zircon is (Zr_1–y, REE_y)(SiO₄)_1–x(OH)_4x–y. Zircon precipitates from silicate melts and has relatively high concentrations of high field strength incompatible elements. For example, hafnium is almost always present in quantities ranging from 1 to 4%. The crystal structure of zircon is tetragonal crystal system. The natural color of zircon varies between colorless, yellow-golden, red, brown, blue, and green.

The name derives from the Persian zargun, meaning "gold-hued".^[10] This word is changed into "jargoon", a term applied to light-colored zircons. The English word "zircon" is derived from Zirkon, which is the German adaptation of this word.^[11] Yellow, orange, and red zircon is also known as "hyacinth",^[12] from the flower hyacinthus, whose name is of Ancient Greek origin.